A two time-slot Time Divide Multiple Address (TDMA) frame structure is used in a Digital Mobile Radio/Police Digital Trunking (DMR/PDT) standard meter, which is divided into uplink and downlink directions. Each time slot is 30 ms, one TDMA frame comprises two time slots, and the uplink and downlink frame structures are as shown in FIG. 1. Each downlink TDMA frame has 2.5 ms Trunk Station Control Channel (CACH) signaling in the center, each two downlink TDMA frames form a multi-frame structure, and each multi-frame contains four CACH signaling.
Data pull-up is that a calling party needs to obtain data of a called party, the calling party initiates a request, the called party gives the data, the calling party receives the data, and an uplink communication device sends downlink signaling to a terminal to pull up, and the terminal will reply the data pulled up on next uplink time slot of the same channel. The uplink and downlink workflows of the terminal and the uplink communication device are as shown in FIG. 2. The terminal sends an uplink request at a point A, and the uplink communication device can perform a downlink response at a point B. The uplink communication device sends a downlink request at a point C, and the terminal can perform an uplink response at a point D.
The current data pull-up is that the uplink communication device sends a pull-up request to a target terminal on a fixed channel, and the terminal responds on next time slot of the same channel, and only one-to-one single pull-up mode is supported. The current data pull-up is generally completed through a control channel or another time slot of the same frequency as the control channel.
The current DMR standard only defines the one-to-one single data pull-up method on the control channel. This method will occupy control channel resources of the uplink communication device, has very low transmission efficiency, and is easy to cause control channel congestion, which will affect other services and cannot support large-capacity and high-frequency data pull-up services. Other existing pull-up schemes can only support that the entire pull-up and reply process are completed on the same channel and time slot, and cannot be dynamically adjusted. Only one terminal can be pulled up at a time and the data is uploaded once. It is not flexible enough to use and the entire channel utilization rate and the pull-up capacity are not high enough.
The communication capacity bottleneck of the current cluster system control channel has become the bottleneck of the terminal access capacity. Especially in applications that need to support large-capacity and high-frequency data pull-up, the communication capability of the control channel seriously affects the number of access terminals. Moreover, the current channel resources are very expensive and scarce, and more optimal allocation and use of limited channel resources are necessary.